Brake control unit

ABSTRACT

Towed vehicles can be extremely heavy. Accordingly, it is too much of a burden to the braking system of a towing vehicle to not have brakes on the towed vehicle. Controlling the brakes of the towed vehicle must be accurately applied otherwise undesirable conditions can be created. There is a need for a method for controlling braking of a towed vehicle. This method comprises receiving a first signal via a communication bus of a towing vehicle, the first signal relating to at least one operating condition of at least one the towing vehicle and a towed vehicle, sending a second signal to brakes of the towed vehicle, the second signal based on said first signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 60/617,062 filed on Oct. 8, 2004, and U.S. ProvisionalPatent Application No. 60/616,979 filed on Oct. 8, 2004, which are bothhereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to a brake control unit, andmore specifically, to a brake control unit that provides a brake outputsignal to brakes of a towed vehicle based on certain inputs received.

BACKGROUND OF THE INVENTION

A variety of prior art brake control units that provide a brake outputsignal to the brakes of a towed vehicle have been proposed and/ormanufactured. Few, if any, of these brake control units, however, usespeed inputs to provide the brake output signal. They are mostly inertiaor pressure based units. Additionally, most current brake control unitsdo not efficiently operate in conjunction with a towing vehiclesanti-lock brake system to create a stable braking event.

On most brake control units if the main input is unavailable, the brakecontrol unit will not function properly. Similarly, if a short occurs inmost current control brake units, the unit will either disables itselfor will shut down, further causing a potentially undesirable situation.And, if a reverse voltage is applied to most brake control units, theywill be disabled. Finally, if an error occurs in the brake control unitor between the communication of the brake control unit and the towingvehicle, most systems do not have a way of notifying the operatorindependent of the brake control unit or storing the error for atechnician's review thereof.

Most current brake control units are not integral with the towingvehicle's instrument panel. They are aftermarket units. They are notable to communicate with and communicate over existing systems withinthe towing vehicle. For example, these units are not able to warn anoperator of an error through the towing vehicle's current warningsystems. They are unable to operate with the rest of the displays on thetowing vehicle's instrument panel.

Finally, most current brake control units are not effectivelyconfigurable or completely operable with a particular towing vehicle.The brake control units are unable to be configured to respond to theidiosyncrasies of a particular vehicle, they are unable to providediagnostic data, they are unable to adjust to conditions in theenvironment or in the towing vehicle, and are unable to providelife-cycle data regarding the brake control unit.

SUMMARY OF THE INVENTION

What is needed is a brake control unit that generates an output signalto the brakes of a towed vehicle directly related to a variety of inputsignals sent from the towing vehicle, the towed vehicle, the operator,or a combination of any of the three. Additionally, it would be helpfulif such brake control unit stores diagnostic code information and otherevents that will assist a service technician in diagnosing failure modesin the brake control unit or other modules with which it interfaces.Finally, it would be helpful if brake control unit includes severalsafety features and redundant procedures built in it to protect againstfailures in the brake control unit, the towed vehicle, or the towingvehicle.

An embodiment of the present invention is directed to a method forcontrolling braking of a towed vehicle. The method comprises receiving afirst signal via a communication bus of a towing vehicle, the firstsignal relating to at least one operating condition of at least one thetowing vehicle and a towed vehicle, sending a second signal to brakes ofthe towed vehicle, the second signal based on said first signal.

According to another embodiment of the present invention, a method forcontrolling braking of a towed vehicle comprises receiving a firstsignal relating to at least one of an operating condition of a towingvehicle, a manual input, and an operating condition of a towed vehicle,the first signal being received via a communication bus of the towingvehicle, sending a second signal to brakes of the towed vehicle, thesecond signal based on the first signal, and sending a third signal tothe towing vehicle via the communication bus, the third signal relatingto the operating condition of at least one of the towing vehicle and thetowed vehicle, and storing the third signal in a memory for diagnosticor life cycle management of a brake control unit.

According to yet another embodiment of the present invention, a brakecontrol unit comprises a processor, a first signal relating to at leastone of an operating condition of a towing vehicle, a manual input, andan operating condition of a towed vehicle, the first signal sent to theprocessor via a communication bus of the towing vehicle, and a secondsignal sent by the processor to brakes of the towed vehicle, the secondsignal based on the first signal.

According to another embodiment, a brake control unit comprises a firstsignal from a towing vehicle's communication bus, the first signalrelating to at least one operating condition of the towing vehicle orthe towed vehicle, a processor capable of receiving the first signal, asecond signal sent from said processor to brakes of a towed vehicle, thesecond signal based on said first signal, a third signal sent to saidtowing vehicle from the processor, the third signal based on a failureof at least one of the towing vehicle, the towed vehicle, and the brakecontrol unit, and memory operably coupled to the processor to store thethird signal.

According to yet another embodiment, a method for controlling braking ofa towed vehicle comprises receiving a first signal via a communicationbus of a towing vehicle, the first signal relating to anti-lock brakesof the towing vehicle, sending a second signal to brakes of the towedvehicle, the second signal based on the first signal releasing thebrakes to prevent wheels of the towed vehicle from locking; andreapplying the brakes of the towed vehicle based on the first signal.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims, andappended drawings.

DESCRIPTION OF THE DRAWINGS

Objects and advantages together with the operation of the invention maybe better understood by reference to the following detailed descriptiontaken in connection with the following illustrations, wherein:

FIG. 1 is an exemplary electrical schematic diagram of the electronicsystem of a brake control unit according to an embodiment of the presentinvention;

FIG. 2 is an exemplary electrical block diagram of a brake control unit,according to an embodiment of the present invention;

FIG. 3 is a front view of a faceplate display of an embodiment of thebrake control unit;

FIG. 4 is a front view of the faceplate display of an embodiment of thebrake control unit integrated with the instrument panel of a towingvehicle;

FIG. 5 is an electrical schematic of a typical connection of a brakecontrol unit without reversed battery protection;

FIG. 6 is an electrical schematic of a reversed connected towing vehiclebattery;

FIG. 7 is an electrical schematic of a reversed connected breakawaybattery with the breakaway switch closed;

FIG. 8 is an electrical schematic of the parts required to preventdamage from reverse connection of either battery;

FIG. 9 is an electrical schematic of the reversed connection of thetowing vehicle battery; and

FIG. 10 an electrical schematic of a reversed connection of thebreakaway battery.

DETAILED DESCRIPTION

A brake control unit for a towed vehicle, e.g., a trailer, disclosedherein generates an output signal to the brakes of the towed vehicle toapply a certain brake load thereto. The output signal is related to avariety of input signals received by the brake control unit from thetowing vehicle, the towed vehicle, the operator, or any combination ofthe three. Additionally, the brake control unit has the capability ofstoring diagnostic information and other events, including error events,in memory in the brake control unit. This information can assist aservice technician in diagnosing failure modes in the brake control unitor other modules such as those of the towing vehicle and/or towedvehicle with which it interfaces. Further, the brake control unit hasseveral safety/performance features and redundant procedures built in toit to protect against failures in the brake control unit, the towedvehicle, and/or the towing vehicle. Finally, the brake control unitdrives the towed vehicle's and towing vehicle's brake lamps directlyduring a manual override braking event. The power to drive the brakelamps comes from a separately fused supply where other brake controlunits use a single supply for all functions.

The present brake control unit can be an original equipment manufactured(OEM) unit that is installed in the towing vehicle at the factory.Alternatively, the trailer brake control unit can be incorporated intothe towing vehicle as an after-market component. The brake control unitcan be installed in the dashboard of the towing vehicle, much like a carradio is. In either embodiment, the trailer brake control unit isintegrated with the towing vehicle as an electronic control device thatprovides variable braking power to electric brakes on a vehicle towed bythe towing vehicle.

More specifically, the brake control unit generates and applies aparticular voltage to the brakes of the towed vehicle so as to apply abrake load to slow-down or stop the towed vehicle. The voltage appliedis related to the input signals available on and/or from the towingvehicle, among other available inputs. Several of these input signalsare diagrammatically represented on FIG. 2. It should be understood,however, that the brake control unit can have other input signalsinputted therein leading to other responsive outputs applied thereto.These additional input signals may come directly from the operator ofthe towing vehicle, from the towed vehicle, or a combination of any ofthe three.

The brake control unit uses a variety of preselected or continuouslymodified algorithms to generate the appropriate output to the towedvehicle brakes based on the received inputs. A processor on the towingvehicle (although it may be located on the towed vehicle) receives theinput signals from the source (such as the ABS system, a speed meter,the ignition, the brake pedal, other processors on the towing vehicle,etc.) and generates the appropriate output signal. The algorithms storedwithin the processor may be updated by having new algorithms enteredtherein or having the existing algorithms modified automatically ormanually. It should be noted that the brake control unit is capable ofbeing reprogrammed meaning that the algorithms stored therein can bemodified by a technician or a completely new set of algorithms may beentered therein by a technician. This allows the brake control unit tobe updated with new information regarding the towing vehicle, the towedvehicle, or the brake control unit itself. The algorithms stored in thebrake control unit correspond to each unique combination of inputs. Theselection of the appropriate algorithm or algorithms is done by theprocessor once it receives the appropriate input information. Further,depending upon changes in the input(s), the processor may select adifferent algorithm or algorithms to generate the appropriate brakeoutput signal. Of course, the processor or a technician/operator mayalter the algorithms stored to generate an appropriate brake outputsignal.

The braking energy provided to the trailer is varied with a pulse widthmodulated (PWM) signal that switches between zero volts and theavailable battery voltage. The higher the duty cycle (more time spent atthe available battery voltage), the more braking power available.Algorithm(s) controlled by the brake control unit determines the brakeoutput signal, for example the PWM output signal, to the towed vehiclebrakes based on information it receives from the towing vehicle, towedvehicle, and/or directly from operator selected settings captured viathe brake control unit, including those captured via the brake controlunit's faceplate display. (The faceplate display is accessible to theoperator by its position in the towing vehicle's instrument panel, whichis discussed in more detail below.)

The brake output signal controlled by the brake control unit based oninformation it receives can be represented as a transfer function. Thistransfer function relating the brake output signal to the various inputsignals can be defined as, for example, by: PWM%=f₁(BPT−BPT_(offset))*f₂(speed)*f₃(gain)*f₄(voltage)*f₅(ABS)*f₆(deceleration)*f₇(brakes-on-off)*f₈(manualoverride)*f₉(redundant brake signal)*f₁₀(time). It should be understood,however, that the transfer function can include any or all of the inputsignals listed above in any manner or combination. Additionally, itshould be understood that the transfer function is not limited to thoseinput signals listed above.

As shown in the electrical block diagram of FIG. 2, the brake controlunit 10 can receive and send signals via a communication bus 20, such asthe high speed controlled area network (HSCAN) bus 20 shown. Forexample, the brake control unit 10 can receive and send signals relatingto wheel speeds of the towing and/or towed vehicle, deceleration,anti-lock brake system (ABS) brake-on-off, etc. The brake control unit10 can also receive signals from the brake pressure transducer 30 (BPT)of the towing vehicle, and can also receive a power signal 40. The brakecontrol unit 10 is grounded 50 as means of protection and safety. Thebrake control unit 10 is also capable of: sending signals to the brakesof the towed vehicle 60; sending signals to the stoplight 70 of thetowed vehicle, including stoplight power 75; sending other signals tothe towed vehicle; and sending signals to the towing vehicle. The brakecontrol unit 10 is also capable of receiving information regarding theignition of the towing vehicle 80.

Further, the brake control unit 10 can include an input/output bufferand filtering device 100. The brake control unit 10 also can include aload dump and reverse connection protection device 110, BPT powerinterface 115, output drivers with current sense and flyback 120, and acommunication bus interface 130. The brake control unit 10 can alsoinclude a voltage regulator and watchdog with reset 140, a stop lightdrive 160, and a power failure advanced notice 170. It should beunderstood, however, that the brake control unit 10 may be alternativelyconfigured and should not be limited to the embodiment shown in thedrawings.

Finally, the brake control unit 10 includes a faceplate display 200,which is shown in FIG. 3. It should be understood that the brake controlunit 10 is not limited to the faceplate display shown in FIG. 3. Anysort of display system can be used. The brake control unit 10 drives thefaceplate display thereof to communicate information such as percentageof brake signal output, gain value settings, and trailer connectivitystatus. In one embodiment, the brake control unit 10 utilizes a display230 for displaying the current gain setting, such as two seven segmentdisplays. The brake control unit 10 may use another display to representthe current brake control output level, such as a ten segment bar graph220 shown in the drawings. Finally, a trailer icon 210 that uses anoperator notification system to indicate a connected and disconnectedstate, e.g., a green state symbolizing the connected state and a redstate symbolizing a disconnected state. In an exemplary embodiment alight emitting diode can be used to indicate the towing vehicleconnected and disconnected state. Finally, the faceplate display mayinclude a manual override control 240, which may have a thumb rest 242,and gain switches 250, which are described in more detail below.

The brake control unit 10 can be fully integrated with the towingvehicle, as shown in FIGS. 3 and 4. This allows the brake control unitto be originally installed equipment in a towing vehicle. In otherwords, the brake control unit can be a factory-installed option on atowing vehicle. In such circumstances, the displays and the controls forthe brake control unit are integrated into the instrument panel 280 ofthe towing vehicle. As such, it is imperative that the controls operatesimilarly to the other controls contained in the towing vehicle'sinstrument panel. In particular, automatic dimming and light harmonywith the dash lighting elements is important.

Accordingly, the brake control unit incorporates a mechanism viasoftware and hardware interface to adjust the lighting intensity of thedisplays to coordinate with the intensity of the dash lighting elementsof the towing vehicle. The adjustment of the brake control unit displayis triggered through a message list being received via the towingvehicle communication bus. This adjustment is controlled throughcommunication with the display driver and the display elements, such asby serial communication. Through a series of commands the functionalityof the display, for example, dimming, blinking, setting element values,scrolling, etc., can be modified. For example, the gain buttons on thebrake control unit are backlit to assist the operator in locating theseadjustment devices. The intensity of the back lighting is also variedbased on the operator's adjustment of the interior dash light adjustmentof the towing vehicle.

In order to operate the components above, the brake control unit 10includes a processor 300. As used herein, the term “processor” mayinclude a general-purpose processor, a microcontroller (e.g., anexecution unit with memory, etc., integrated within an integratedcircuit), a digital signal processor (DSP), a programmable logic device(PLD) or an application specific integrated circuit (ASIC), among otherprocessing devices. The processor must have enough on-board memory tocontain the software requirements to communicate with the towingvehicle's communication bus (such as the CAN or a high-speed controlledarea network (HSCAN)), or other communication systems (such as a localinterconnect network (LIN) and a J1850), in-vehicle diagnostics, andrequired functionality for interpreting vehicle and driver inputs. Itmust also have the capabilities to provide proper control to the: brakesof the towed vehicle, towing vehicle stop lamps during a manual brakingevent, towed vehicle stop lamps during a manual braking event, andfaceplate display information accessible to the operator. Further, asshown in FIG. 2, the processor 300 is operably coupled to a displaydriver 305, a manual control override 310, and gain up/down switches320. The display driver 305 is operably coupled to the LEDs for trailerconnect and disconnect 325 (discussed in more detail below) and a bargraph display and dual seven segment display 330. It should beunderstood that alternative configurations are also contemplated herein,not just that shown in the drawings.

The exemplary electrical schematic diagram of the brake control unit 10is shown in FIG. 1. It should be understood that the configuration ofthe brake control unit in FIG. 1 is an embodiment of the brake controlunit, and that alternative embodiments of the electrical schematicdiagram are also contemplated herein.

As previously stated, the brake control unit generates an output signalbased on a variety of information received from the towing vehicle (aswell as other information from the operator and the towed vehicle). Thistowing vehicle information can be received through hard-wired inputsfrom a brake pressure transducer, a brake on-off switch, and an ignitionrun line, as shown in FIG. 2. Additional vehicle provided informationcan be received through the towing vehicle's communication bus.Although, towing vehicle information from the brake pressure transducer,brake on-off switch, and ignition line can also be received through thetowing vehicle's communication bus. Among the information received viathe towing vehicle's communication bus is the redundant brake signalstatus, the brake on-off status, ABS event in progress flag, wheel speeddata, vehicle deceleration data, and dimming information for thefaceplate display. Most signals received by the brake control unit willbe “debounced,” meaning that in order for the brake control unit tooutput a signal based on the input, it will receive more than one suchinput signal. It is used to verify each signal so that one rogue signalwill not inadvertently alter the brakes of the towed vehicle. The brakecontrol unit also sends out information on the brake control unit systemstatus via the towing vehicle's communication bus. These messages aredisplayed on the instrument cluster message center in the towingvehicle.

One of several input factors used to effectively apply the brakes of thetowed vehicle by, e.g., obtaining the appropriate voltage to apply tothe brakes of the towed vehicle, is a speed signal. As electric brakesare speed dependent in their operation to most effectively andefficiently operate the brakes speed must be considered and accountedfor. The speed signal may be received from the towing vehicle or eventhe towed vehicle via a speed meter, such as a global positioning system(GPS) receiver, a wheel speed sensor, an engine speed sensor, a throttleposition sensor, a Doppler sensor, etc. Alternatively, the speed signalmay be received from the speedometer of the towing vehicle. Theappropriate algorithm or algorithms stored in the processor apply thisspeed signal and in response modify the voltage to the towed vehiclebrakes. For example, the brake control unit will apply greater voltagesto the brakes of the towed vehicle at higher speeds to compensate forbrake inefficiency and will apply reduced voltages at lower speeds tocompensate for the aggressive nature of electric brakes at low speeds,e.g., speeds below 15 mph. The appropriate algorithm or algorithms arebased on not only the speed, but also the efficiency of the particularbrakes. This allows for more effective and efficient braking. The BPTinput signal can be received via the towing vehicle's communication busor through hard-wired inputs.

Additionally, the brake control unit can receive an input signal fromthe brake pressure transducer (BPT). This input signal represents thebraking effort by the operator. When the brakes of the towing vehicleare not active (pressed), there is certain offset voltage present on theoutput of the BPT. This offset voltage needs to be nulled to determinethe input signal representative of the braking effort. The offset signalis acquired when the brake control unit is in the idle mode. In thismode, there is no manual or automatic braking event. Several samples areacquired and averaged to determine the offset voltage. During anautomatic braking event, the BPT input voltage is sensed and the offsetvoltage is subtracted from it.

A performance feature of the brake control unit is that it can detect afailure of the BPT. In this situation, the brake control unit will sensethe voltage supplied by the BPT when the brake-on-off switch (stoplightswitch) or the redundant brake signal indicates an active braking. Ifthis voltage is lower than or the same as the offset voltage, a failureof the BPT has occurred (there is no pressure in the BPT) and the eventis reported, e.g., storing such event as part of the diagnosticinformation.

The brake control unit can also receive an input signal from the towingvehicle's anti-lock braking system (ABS) so as to adjust the applicationof the towed vehicle's brakes. In particular, the algorithm applies theABS signal of the towing vehicle and responds to that signal by alteringthe brakes of the towed vehicle based on the ABS event. For example, thealgorithm can cause the towed vehicle to continue to fully brake if theABS is triggered due to wheel slip on a high μ surface, or can be usedto reduce the braking to the towed vehicle if the ABS condition resultsfrom braking on a low or split μ surface. Using the ABS signal allowsthe total braking event to become more stable. Alternatively, the brakecontrol unit may use a speed signal and/or accelerometer as an input toprovide a stable braking event as described below.

More specifically, when an ABS event occurs on the towing vehicle orwhen the speed signal input or accelerometer input indicate, the brakecontrol unit will attempt to provide stable braking. It may firstrelease the brakes to ensure that the towed vehicle wheels are notlocked. Then it may reapply the towed vehicle brakes based on adeceleration input, e.g., a signal supplied from the ABS system over thetowing vehicle communication bus. This strategy may remain in effectuntil the brake event has ceased, or until the ABS event has ceased.

Further, the brake control unit is aware of the absence or invalidity ofthe ABS signal and deceleration signal and stores the diagnosticinformation thereof. If the ABS signal and/or deceleration signal areabsent or invalid, the brake control unit uses a proportion of the BPTsignal, such as 50%, to reduce the power to the brakes of the towedvehicle to prevent the wheels of the towed vehicle from locking in casean ABS braking event is occurring.

The brake control unit can also receive the vehicle identificationnumber (VIN) from a particular towing vehicle and configure itself basedon that particular vehicle's variables, such as its brake systems,stability systems, wheel base, 4×4, 2×4, GVW, etc. The towing vehiclecan store the VIN in its memory. The brake control unit can receive thisinformation from the towing vehicle via its communication bys. Based onthe VIN, the brake control unit uses its algorithms stored in theprocessor (or can modify such) to configure the towed vehicle's brakes(including their braking curve) based on the variables of the towingvehicle with that particular VIN. The brake control unit can alsoconfigure itself based upon variable of the particular towing vehiclewith that particular VIN.

The brake control unit can receive a signal from the towing vehicle thatconfirms whether or not such towing vehicle is configured to functionwith a brake control unit or with the particular brake control unitinstalled. The brake control unit can use the VIN, or alternatively, canuse other information provided by the towing vehicle. This signal issent over the towing vehicle's communication bus. If the brake controlunit receives this signal from the towing vehicle, the brake controlunit can notify the operator and will shut itself down to preventunauthorized use.

Another input signal that can be sent to the brake control unit iswhether the ignition of the towing vehicle is on or off. The brakecontrol unit uses at least one algorithm stored in the processor that isbased on sensing the ignition of the towing vehicle or the lack thereof.The ignition input signal can also be used as part of the sensing for asleep mode of the brake control unit. In the sleep mode the idle currentcan be minimized for the brake control unit to minimize the drain of thebattery on the towing vehicle. In other words, when the ignition of thetowing vehicle is turned off, a signal is sent to the brake control unitvia the communication bus instructing the brake control unit to go intoa sleep mode. In this sleep mode, the brake control unit drawssignificantly less voltage. The ignition signal going to high, or on, isused to wake up the brake control unit. In this case, when the ignitionis turned on, the brake control unit is awakened. It will drawsufficient voltage to be completely active. An alternative method forwaking the brake control unit up is to base it on towing vehiclecommunication bus activity. The brake control unit can be programmedsuch that any towing vehicle communication bus activity can wake up thebrake control unit. As with the ignition on-off, when there is little tono towing vehicle communication bus activity the brake control unit goesinto a sleep mode. This also minimizes the idle current down to themicroampere level. When communication bus activity resumes, the brakecontrol unit is awakened.

Additionally, the brake control unit has access to the park, reverse,neutral, drive, and low gear signals of the transmission of the towingvehicle to further modify the brake output signal. Again, algorithmsstored in the processor can be altered and/or a particular algorithm(s)selected based on this additional input. This is useful because towedvehicle brakes do not have the same braking efficiency in reverse asthey do in forward. For example, if the towing vehicle is in reverse, asignal is sent to the brake control unit notifying of such reversecondition. Then, the brake control unit sends a brake output signal toapply more voltage to the brakes so that they may be applied moreaggressively. Therefore, the algorithms can be adjusted based on thisinformation to effectively and efficiently apply the brakes for thecurrent gear setting.

Another input signal that can be used to adjust the braking output isthe powertrain load of the towing vehicle. The load on the powertraincan be used to help determine the total load (weight) of the combinationof the towing vehicle and the towed vehicle. This information isinputted from the appropriate sensor into the appropriate algorithm toconfigure the brake control unit to have an improved braking performancebased on the actual weight of the towing vehicle and towed vehicle.

In addition to automatic inputs, the brake control unit can use inputsmanually entered from an operator to control the output of the towingvehicle brakes by using predetermined algorithms, modifiable algorithms,or both. In particular, an operator can manually enter an input and thebrake control unit can output a brake output signal that can apply thebrakes of the towed vehicle in a predetermined manner based on suchinput.

One operator input available is the gain buttons, which may be presenton the faceplate display of the brake control unit. The gain buttons canprovide several different inputs to the brake control unit. For example,holding the gain buttons simultaneously with the brake-on-off activeinput may allow the brake control unit to change its configuration toallow the algorithm to convert from electric brake curves to electricover hydraulic algorithms (or brake curves). Other operator interfacecontrols of the brake control unit can be used in combination to achieveother means to alter configurations of the brake control unit. Since theload sensing and performance curves are significantly different for thetwo types of braking systems, this allows for adapting the brake controlunit via the operator input to a unique algorithm(s) for electric overhydraulic brakes. Also, the display can show the use of the alternateconfigurations to notify the operator of the configuration currentlyset. For example, a flashing digital character representation may showthat the brake control unit is interfacing to an electric over hydraulicbraking system.

Another input the gain buttons can provide is to adjust the maximum dutycycle available. More specifically, if manual activation occurs during anormal or ABS braking event the greater of the two duty cycles, i.e., anormal ABS event or a limited operating strategy (LOS) decelerationbraking event, is used. The determined duty cycle is then adjustedaccording to the current gain setting. The gain setting is used as amultiplier to the duty cycle. Therefore, it will produce an output thatis scaled to a certain percentage of the current braking level theoperator is requesting. For example, if the operator is requesting 75%desired braking capacity at a gain setting of 6.0, the brake controlunit will provide 45% of the maximum duty cycle available (60% times75%).

Additionally, along with the gain setting the reference speed isinputted into a transfer function. This scales the gain adjusted dutycycle output according to the towing vehicle speed. At low speeds, ascaled percentage of the brake output signal is computed based on thecurve that is present in a lookup table present in the processor. Thisthereby causes reduced braking strength at lower speeds to prevent thebrakes of the towed vehicle from jerking. At higher speeds, the brakeoutput signal is set to 100% of calculated duty cycle. This duty cyclevalue is stored to be used for the output display on the brake controlunit console. The unadjusted value of this signal is used to drive thebar graph display on the brake control unit console, thereby,communicating to the operator the total level of braking requested at aspecific gain setting.

As showing in FIG. 3, the present embodiment of the brake control unituses two separate buttons, one to increase and one to decrease the gainsetting. Pressing each button activates its own momentary push switch.It should be understood, however, that any number of buttons can be usedherewith. Additionally, any sort of device can be used, not just thebuttons shown. For example, one could use a slide, knob, touch-screen,etc.

Another operator input that is present on the faceplate of the brakecontrol unit is a manual override control. The manual override controlcan be, e.g., a manual slide having a linear travel potentiometer,controlled by the towing vehicle operator. In this embodiment, themanual slide can be part of the brake control unit faceplate and isspring-loaded to an at rest (inactive) position. This input to the brakecontrol unit allows the operator to manually apply towed vehicle brakeswithout having to depress the brake pedal. The manual override controlis mainly used in conjunction with the gain adjustment buttons describedabove to calibrate maximum towed vehicle braking available based onspecific towed vehicle loading, towed vehicle tire and brake conditions,and road conditions. Normal maximum is that braking force that is justshort of causing the wheels of the towed vehicle to skid. When theoperator activates the manual override control the brake control unitsends a signal over the communication bus to the towing vehicle.Additionally, whenever there is an automatic braking event, e.g., theoperator depressing the brake pedals of the towing vehicle, a signal isalso sent to the towing vehicle from the brake control unit via thecommunication bus.

In order to communicate between the towing vehicle, the towed vehicle,and the brake control unit, the brake control unit utilizescommunication bus methods. The brake control unit extracts data from thetowing vehicle's bus as well as transmits information to the towingvehicle's bus to interface with other subsystems in the towing vehicle,e.g., cluster, ABS, vehicle stability systems, transmissions, dimmingfeatures, etc. The brake control unit is in constant communication withthe towing vehicle's communication systems and can alert the operatorand other vehicle systems of operation, lack of operation, defects foundwithin the interfacing systems, etc. In particular, the brake controlunit receives and sends messages over the towing vehicle's communicationbus interface. The trailer brake controller periodically transmitsstatus message information over the towing vehicle communication businterface. These messages include diagnostic messages, data interfacesto other modules of the towing vehicle, and informational and alertmessages to the cluster, which in turn displays visual alerts andinitiates audible alerts.

In addition to the communication bus above, the brake control unit canalso receive a measure of the brake pressure from a brake pressuretransducer mounted to the master cylinder of the towing vehicle. Thebrake control unit can also receive inputs from an operator interface,including a set of gain switches and a manual brake apply lever, whichindependently actuates the towed vehicle's brakes.

Integrating the brake control unit with the towing vehicle'scommunication system using the towing vehicle's communication bus alsoallows information relating to the brake control unit, the towingvehicle, and the towed vehicle to be stored. For example, brake controlunit diagnostic code information and other events that can assist aservice technician in diagnosing failure modes in the brake control unitor other modules (including those of the towing vehicle) it interfaceswith can be stored.

The brake control unit collects and stores information in memory, forexample in electrically erasable programmable read-only memory (EEPROM)or Flash memory, to allow for diagnostics, life cycle management, etc.of the brake control unit, the towing vehicle, and/or the towed vehicle.More specifically, the brake control unit can read and store the numberof ignition cycles, the gain adjustments, number of manual activations,the VIN of the towing vehicle, calibration data, other defect codesduring the life of the brake control unit, serial number of the brakecontrol unit, date of manufacture of the brake control unit, and otherconfiguration management data of the brake control unit. Thisinformation is useful in understanding the life of the brake controlunit as well as representing the conditions the brake control unit hasbeen subjected to throughout its life. For example, storing the serialnumber of the brake control unit helps traceability of the unit itselfas well as the components that make up the unit. This helps with theserviceability of the unit and its components. Additionally, thediagnostic section determines if a valid fault exists. If it does, it isstored in memory. Again, this assists a technician with maintenance ofthe brake control unit. Finally, depending on the severity of the faultthe towing vehicle may be notified that a serious fault exists thatcould hinder the normal operation of the brake control unit. The towingvehicle will notify the operator of such fault occurring. If the faultis not severe, it is merely stored in memory to be accessed by atechnician at a later time.

Many specific codes can be used with the brake control unit to allow itto diagnose other subsystem failures of the towing vehicle, towedvehicle, and brake control unit and report this information back via thecommunication bus so the complete towing vehicle, brake control unit,and towed vehicle can be diagnosed. The brake control unit has completeself-diagnostics as well as diagnostics for interfacing with othercomponents of the towing vehicle and towed vehicle, such as brakepressure transducer, ABS system, brake on-off, cluster instrumentpanels, vehicle stability system, and power distribution. This allowsfor real-time troubleshooting and adjustments to algorithms forperformance based on the diagnostic capabilities built into the brakecontrol unit. More specifically, the brake control unit can, based uponthe diagnostic information received from the towing vehicle or towedvehicle, adjust the algorithms stored therein to optimize its operation.For example, the brake control unit can receive diagnostic informationregarding the ABS system of the towing vehicle and can adjust the brakeoutput signal to account for the specific operation of the ABS system.

In an embodiment, the brake control unit uses memory to storeinformation relating to every ignition cycle of the towing vehicle. Thestorage and usage of this information generated in such a manner thatminimizes the storage size so a small microprocessor can be used, forexample a Motorola Mc68HC908AZ32A. The brake control unit utilizes astorage array as a fixed area of memory within which may exist a numberof ignition configurations. The ignition configuration is a variablelength stored data grouping for a specific vehicle ignition cycle andincludes an end of configuration marker. After several ignition cyclesthere will be several ignition configurations stored. Each will followthe previous ignition configuration then wrap back to the beginning ofthe storage area when the end of the storage array has been reached. Atstart-up the brake control unit looks for the end of configurationmarker that is always written at the end of the latest configuration.This configuration is then used to initialize the current operatingvariables and diagnostic information of the brake control unit. Thecurrent configuration overwrites the previous end of configurationmarker with a new ignition configuration. For example, the most currentignition cycle configuration is followed with two or more bytes ofstorage in their erased state. At a power on/reset event the presence oftwo or more bytes of storage in their erased state would identify themost current ignition configuration. The number of valid ignition cyclesis stored in an ignition configuration as an increment of the valuestored during the previous valid ignition cycle.

In addition to the number of valid ignition cycles, operatingcharacteristics of the brake control unit, such as the gain setting,operating characteristics of the towing vehicle, operatingcharacteristics of the towed vehicle, the number of diagnostic failures,and the diagnostic failure information can be stored in the ignitionconfiguration. The diagnostic failure information includes the failurethat occurred, the number of ignition cycles such failure occurred, andthe number of ignition cycles since the last occurrence of such failure.Each ignition configuration also includes a checksum to assist inidentifying good or incomplete/incorrect data stored in a specificignition configuration. A technician can then access the informationstored in the ignition configuration to diagnose any problems with thebrake control unit, towing vehicle, or towed vehicle.

When the diagnostic mode of operation has verified that certain specificfaults have occurred, a limited operating strategy, which is describedin more detail below, is entered. The diagnostic mode runssimultaneously with the operational modes of the module. It runs asystem of tests to verify certain faults that have occurred duringnormal operations and also determines whether the module should enterthe limited operating strategy.

The brake control unit includes several performance features and safetycharacteristics built therein. For example, the brake control unit has aredundancy built into it. This redundancy is a limited operatingstrategy (LOS). It allows the brake control unit to continue to functiondespite the main input (e.g., brake pressure transducer) beingunavailable. This permits the brake control unit to give the operatorthe ability to brake at a comparable deceleration mode to the currentcontrols despite losing the main input. It, also, notifies the operatorof the error and notifies the operator to seek out the closest dealerand address the problem. In an embodiment of the current brake controlunit, BPT is the primary input, deceleration is the secondaryredundancy, and the final default would be a time-based output as athird means for redundancy. In the situation in which BPT has failed,the deceleration signal from the communication bus is used to calculatethe brake output signal, which can be represented as: PWM%=f₅(deceleration)*f₂(speed)*f₃(gain)*f₄(voltage). If the decelerationsignal is unavailable, a time-based output is used to calculate thebrake output signal, which is defined as follows: PWM%=f₆(time)*f₂(speed)*f₃(gain)*f₄(voltage). This will allow the brakes ofthe towed vehicle to active despite failures of the BPT, ABS, and/orcommunication bus.

Another performance feature is that the brake control unit automaticallyadjusts its output based on variable inputs from the vehicle. The brakecontrol unit continuously samples the supply voltage and will adjust itsalgorithm to keep the brake control unit voltage output consistent evenwith variations in the supply voltage. The algorithm will adjust theduty cycle of the PWM to maintain a constant energy to the towed vehiclebrakes. For example, the brake control unit will continually monitor thesupply voltage of the towing vehicle to ensure that such voltage iswithin a normal range. If the supply voltage is lower than normal, e.g.,from a loss of the alternator, then the PWM is increased to maintain aconstant output energy to the brakes of the towed vehicle.

Another performance feature included in the brake control unit isinductive and resistive load sensing for detecting proper loads of thebrakes of the towed vehicle. The brake control unit monitors the currentin the towed vehicle's brake line over a predetermined time, forexample, every four seconds, to determine if the load that is presentrepresents a normal electric towed vehicle brake system. The primaryfeature of the brake magnets is that it has a certain range ofresistance and inductance. Accordingly, the brake control unit performsthe resistive test more quickly, for example every 4 milliseconds,instead of the time that it takes for the inductive test. The resistivetest verifies that the resistance of the load is within range. Theresults of the resistive test are further “debounced” to make sure thatone erroneous reading is not counted. It then conducts the inductiveload sensing to confirm that the load present has inductive value withinrange. The feature of the inductive load that is used is its exponentialcurrent rise with a step input voltage. The resistive test is performedevery loop cycle, regardless of connectivity status. The purpose of thistest is to expedite the indication of an open load, if one exists,within a specific time, e.g., 4 msec, after it occurs. Normally, theinductive test is performed if the resistive test passes every setperiod of time, e.g., 4 seconds, when the resistive test has indicatedthat the trailer is connected. In the case that the resistive testindicates a disconnected load for the first time after having shown aconnection in the past, this triggers an immediate inductive test. Thisis done because the resistive test requires significantly less currentthan the inductive test and does not cause the towed vehicle brakes toapply. The inductive test finally determines the connectivity status ofthe towed vehicle. However, during a braking event, all tests aresuspended to prevent interference with the trailer brake control output.Regardless of the outcome of the inductive/resistive tests, the brakeoutput signal is applied to the towed vehicle brakes during a brakingevent.

If the inductive test determines the presence of a normal load, it isindicated to the operator via a display on the faceplate of the brakecontrol unit, such as trailer icon being lit green. It will alsoindicate when the towed vehicle load is present and the towed vehiclebrake control is active. If the towed vehicle becomes disconnectedduring a dynamic state, such as while towing vehicle is moving above acertain speed (or moving at all), a display, such as a trailer iconflashing red continuously, notifies the operator of such condition. Thetowing vehicle is notified of such condition and the display on theinstrument panel is activated and the cluster sounds a chime toimmediately notify the operator. If the towed vehicle becomesdisconnected during a static state, such as unplugging the towed vehiclewhile it is standing still, the icon flashes for a predetermined time,for example approximately 30 seconds, then shuts off. No chime is setsince it is assumed to be a normal condition. However, the operator isstill notified of the event in case someone inadvertently removed theconnection.

The initial start-up status or default status for the towed vehicle uponstart-up is “trailer not connected.” From this status, if the inductivetest output passes, the module will enter the “trailer connected” state.If, on the other hand, the inductive test output fails while in the“trailer connected” state, the module will enter the “trailerdisconnected” state. If the inductive test output passes while in thisstate, the module will revert back to the “trailer connected” state. Ifmore than one of these conditions exists, therefore sending multiplemessages to the cluster, the cluster will prioritize the messages. Whena “trailer disconnected” state exists, the brake control unit willdetermine what sort of disconnection has occurred, a static or dynamicdisconnection. In the static disconnection state, the towing vehicle istraveling below a minimum speed. In the dynamic disconnection state, thetowing vehicle is traveling above the minimum speed. It should beunderstood that the minimum speed may be zero so that any movementtriggers a dynamic disconnection state.

Another performance feature is that the brake control unit integrates ashort circuit protection for both the towed vehicle brake output lineand the stop lamp drive output line. Both circuits are continuouslymonitored and are protected in the event a short on either of theselines exists. The short circuit sensing is continuous and automaticallyreactivates in a normal mode of operation once the short is removed. Theinput power voltage is monitored. When the control signal to the inputof the POWER MOSFET is activated, the input power voltage is monitoredto sense a sag in it. If this sag crosses a predetermined threshold,e.g., 50%, a shorted condition will be determined. In case of the stoplamps, there is a delay before this sag in input power supply voltage issensed. The reason for this is the inrush currents in the incandescentstop lamps typically used in the automobiles lasts for a varying time,e.g., about 50 msec or more depending on the temperature. Alternatively,the output voltage can be sensed and compared with the power supplyvoltage before turning the stop lamps on.

The circuitry is also designed to identify if the stop lamp circuit isto be driven by the brake control unit if the manual override control isactivated, or through the brakes-on-off circuit on the towing vehicle.There is constant sensing of the brakes-on-off line and a decision ismade if the brake control unit is to drive the brakes-on-off line highor shut down its drive to the brakes-on-off line if the manual overridecontrol mode is engaged. There is only one source to supply thebrakes-on-off line so there is only one current source for the stoplamps.

The stoplights of the present embodiment are driven from a dedicatedvoltage input, separately fused, where most brake control units drivethe stoplights from a common voltage input with the brake output power.The current from most common sourced voltage input can be significantenough to cause opening of a circuit breaker or a fuse rendering thebrake control unit inoperative. The dedicated input of the present brakecontrol unit, on the other hand, eliminates the additional current drawfrom the main voltage input.

Similarly, the incorporation of the field effect transistor (FET) in thebrake control unit output line allows for protection against thedestruction of the circuit due to a reverse polarity situation on theprimary supply. It also protects against a reversed breakaway batteryinstallation on the towed vehicle, which puts a negative 12 volts backonto the towed vehicle brake output line of the control brake unit whena breakaway switch is pulled. Normally a diode is placed across thetowed vehicle brake output line to ground to maintain the brake magnetcurrent in the off time of the PWM. This same diode becomes forwardbiased in a reverse breakaway battery application and places 12 voltsacross the diode and destroys the diode and the circuit board. The useof the FET allows for opening of the ground line during abnormalconditions protecting the brake control unit and allowing for passing ofthe brake current under normal operations without sacrificing voltagedrop or heating.

FIG. 5 is a typical connection of a brake control unit without reversedbattery protection. This figure shows the output stage (U1) of thatbrake control unit in which a single VN920 high side switch made by STElectronics is used. Other optional configurations may include using twoor more VN920s in parallel, one or more power MOSFETs in parallel, orone or more power transistors in parallel. U1 delivers a PWM (PulseWidth Modulated) drive to the brake magnets L1 and L2. (Most towedvehicles use from 2 to 8 magnets in parallel.) The frequency of thissignal is usually in the 200 Hz to 400 Hz range with a duty cycleranging from 0% to 100%.

While U1 is on, battery voltage is applied and current builds up in themagnet. While U1 is off, the current established in the magnetscontinues to flow through D1. The duty cycle times the battery voltageis the effective voltage applied to the brake magnets. The current doesnot continue to increase because each magnet has a resistance of about 4ohms due to the resistance of the copper wire.

Most towed vehicles have a breakaway system to apply voltage to themagnets in case the towed vehicle becomes disconnected from the towingvehicle. S1 is the switch that connects BAT2 to the magnets. BAT2 issized to provide braking for about 15 minutes. This stops the towedvehicle and keeps it from rolling until chocks or such can be placed infront of the tires.

FIG. 6 shows a reversed connected towing vehicle battery. As can beappreciated D1 and the substrate diode in U1 provide a very lowresistance path for current to flow. Typically the brake control unitand or the wiring are destroyed. This can occur when installing thebrake control unit or when installing the battery in the towing vehicle.

FIG. 7 shows a reversed connected breakaway battery with the breakawayswitch closed. D1 is now forward biased by the battery causing highcurrent to flow, which normally results in damage to the control andwiring.

FIG. 8 illustrates the parts required to prevent damage from reverseconnection of either battery. The MOSFET Q1 is a high current MOSFETcapable of handling the currents of normal operation. The major currentis the fly back current from the magnets. It can reach 24 amps with 8magnets. Q1 is biased full on by the connection of the gate to 12.6volts through R1. This keeps the on resistance below 10 milliohms forpreferred MOSFETs. This resistance dissipates very little power duringoperation. It will be noticed that Q1 serves as a controlled switchisolating the circuit ground from chassis ground when the switch is off.

FIG. 9 depicts the reversed connection of the towing vehicle battery. Inthis case the gate is biased at or below the Q1 source voltage and so Q1is off and the circuit is protected from heavy current. If the towedvehicle is connected current will flow through the magnets and thesubstrate diode in U1. This current will be limited to a safe level bythe magnet resistance.

FIG. 10 shows reversed connection of the breakaway battery. In this casewhen SW1 is closed a spike of heavy current will flow. This current willdevelop a voltage drop across the on resistance of Q1. The dividervoltage formed by R2 and R3 will reach the base-emitter voltage of Q2when the current is at the desired trip point. When Q2 starts to turn onthe gate of Q1 is pulled down. This results in the drain voltage risingand provides a snap action with the positive feedback.

Another safety routine is to determine stuck operator inputs, such asthe gain button scroll and stuck manual override control (e.g., stuckmanual slider routine). These allow for continuous sampling of inputsthat should normally be activated by the operator to determine if theinputs are real or if a mechanical or electrical failure has occurred.The sampling routine of the + and − gain buttons, along with thevariables of ignition, brake-on-off, speed, and manual input allow fordetermination of the inputs being legitimate and indexed accordingly orto disable this section of the brake control unit and default back to aprior setting. A notification is then sent to the operator regarding theerror. A stuck gain button could result from a mechanical or electricalfailure. This could lead to continuous cycling of the gain without brakeactivation. This could also result if something was moving inside thecab of the towing vehicle and was pressing against the control. When theoperator depresses a gain button, until the gain limit is reached andthe operator continues to hold it for a period of time, the gain settingwill return to the value prior to the change. A depressed and held gainbutton scrolls through settings until released or until the maximum orminimum value has been attained. The selected gain setting is stored inmemory, e.g., EEPROM or Flash/memory, for future use.

A diagnostic feature for operator inputs is a manual override controlinput, e.g., a manual slider input, sensing for out-of-range (high andlow out-of-range) and in-range. The software and hardware used for thisallows for the determination of a fault mode, out-of-range, that putsthe brake control unit into a potential brakes-on-all-the-time mode, orlow to no-brakes with the manual invoked. The out-of-range allows forflagging internal part issues that may arise due to components,manufacturing, assembly, etc.

Additionally, the brake control unit includes stuck manual overridecontrol input sensing. This permits notification to the operator of thetowing vehicle of potential hazards of a stuck manual override controlinput while the manual input is in-range and allows for an alternativealgorithm that shuts this portion of the brake control unit down untilthe problem has been resolved. These safeguards will prevent damage toor destruction of the brakes of the towed vehicle in the event that thebrake output signal says it should be active when it should not be. Thebrake control unit samples this input along with the speed input toallow for an accurate decision to be made regarding this condition. Thestuck manual override control, e.g., stuck slider position, is saved inmemory, e.g., EEPROM or flash memory, during an ignition configurationso that during a subsequent ignition cycle, the stuck manual overridecontrol, e.g., stuck manual slider, fault will remain active.

Additionally, the brake control unit determines the present mode ofoperation of the control system. The modes are: power-up (wake-up),power-down (sleep), normal operations, diagnostics (limited operatingstrategies), and test. Upon turning on the towing vehicle, the brakecontrol unit determines the present mode of operation by using softwarestored on the processor's memory. During operating of the brake controlunit, it will continually determine the present mode of operation untilthe brake control unit is powered down.

In the power down mode, the brake control unit prepares to shut down andstop execution. The ignition voltage is verified to be below a thresholdto continue the shut down procedures. The brake control unit output isthen disabled, the display is shut down and any diagnostic data isstored in memory and/or reported over the communication bus. Uponcompletion of these the power supply shutdown is initiated, the brakecontrol unit is set into low power mode and the processor is issued astop instruction shutting it down until the brake control unit ispowered on again. The shut down is implemented using, for example, thesystem basis chip (SBC). The processor on detection of low ignitionsignal and after finishing all housekeeping functions sends a serialcommand to SBC to further shut down the process. The brake control unitinitiates a power down sequence by disabling the brake control unitoutput, brake lamp control, and all brake control unit console displayindicators are turned off, e.g., trailer icon, gain displays, and thebar graph. A flag is set in this state for modeling the power up/downstrategies within the module. The power down mode can also be activatedby inactivity on the communications bus. Alternatively, the power downmode can be activated solely by inactivity on the communication bus.

Once in the power down mode, the brake control unit will wake up afterdetecting a positive transition on the ignition input. For example, thiscan be done via the SBC. The SBC can also be woken up by activity on thecommunications bus. Alternatively, the wake up can occur solely byactivity on the communication bus.

The brake control unit also includes a feature that detects when thesoftware has entered an unintended operating condition and fails tofollow a program code, e.g., program runaway, and resets the system foran orderly power up. This can be accomplished by including a device,such as a power-management chip or an SBC, in the brake control unit.The power-management chip must periodically receive a signal, such as aserial command, from the processor. In absence of this signal for apre-determined period of time it will reset the whole system and properoperation will resume.

Modification of the invention will occur to those skilled in the art andto those who make or use the invention, including, without limitation,the values provided for the various elements disclosed above. It shouldbe understood that such values are exemplary values and the presentinvention is not limited to those values. Therefore, it is understoodthat the embodiments shown in the drawings and described above aremerely for illustrative purposes and not intended to limit the scope ofthe invention, which is defined by the following claims as interpretedaccording to the principles of patent law, including the Doctrine ofEquivalents.

1. A method for controlling braking of a towed vehicle, said methodcomprising: receiving a first signal via a communication bus of a towingvehicle, said first signal relating to at least one operating conditionof at least one of said towing vehicle and a towed vehicle; and sendinga second signal to brakes of said towed vehicle, said second signalbased on said first signal.
 2. The method of claim 1, further comprisingsending a third signal to said towing vehicle via said communication busto interface with other subsystems in said towing vehicle, said thirdsignal based on at least one of said first signal and said secondsignal.
 3. The method of claim 2, further comprising generating a brakeoutput signal to said brakes of said towed vehicle based on said secondsignal.
 4. The method of claim 3, wherein said first signal is receivedby a processor from at least one source.
 5. The method of claim 4,wherein said at least one source comprises at least one of a brakepressure transducer of said towing vehicle, a brake-on-off line, towingvehicle interior lighting, memory of said towing vehicle, transmissionof said towing vehicle, powertrain of said towing vehicle, an anti-lockbrake system of said towing vehicle, a speed meter, an ignition of saidtowing vehicle, a speedometer of said towing vehicle, and a brake pedalof said towing vehicle.
 6. The method of claim 5, wherein said secondsignal is based upon algorithms stored within said processor.
 7. Themethod of claim 1, further comprising receiving a signal from a brakepressure transducer of said towing vehicle.
 8. The method of claim 7,wherein said second signal is based on said first signal and said signalfrom said brake pressure transducer.
 9. The method of claim 1, whereinsaid at least one operating condition comprises at least one of speed ofsaid towing vehicle, speed of said towed vehicle, said towing vehicle'santi-lock brakes, vehicle identification number of said towing vehicle,condition of an ignition of said towing vehicle, gears of a transmissionof said towing vehicle, and powertrain load of said towing vehicle. 10.The method of claim 1, further comprising receiving a manual inputsignal from an operator of said towing vehicle, wherein said secondsignal is based on said manual input signal and said first signal. 11.The method of claim 10, wherein said manual input signal comprises atleast one of gain setting and boost setting.
 12. The method of claim 1,further comprising collecting and storing information in a memory toallow for diagnostics, life cycle management, and variables for futureuse.
 13. The method of claim 12, wherein said life cycle managementincludes at least one of number of ignition cycles of said towingvehicle, gain adjustments, number of manual activations, vehicleidentification number of said towing vehicle, calibration data of saidtowing vehicle, calibration data of a brake control unit, date ofmanufacture of said brake control unit, configuration data of said brakecontrol unit, and calibration data of said towed vehicle.
 14. The methodof claim 1, further comprising interfacing with components of saidtowing vehicle to diagnose said components of said towing vehicle. 15.The method of claim 14, wherein said components of said towing vehiclecomprises at least one of brake pressure transducer, anti-lock brakesystem, brake on-off, cluster instrument panels, stability system, andpower distribution.
 16. The method of claim 1, further comprisingreceiving a signal from a brake control unit, said signal from saidbrake control unit relating to operating conditions of said brakecontrol unit.
 17. The method of claim 16, wherein said operatingconditions of said brake control unit includes at least one of serialnumber of said brake control unit, configuration of said brake controlunit, date of manufacture of said brake control unit, and components ofsaid brake control unit.
 18. The method of claim 1, further comprisingreceiving a signal from said towing vehicle relating to detection ofsaid ignition of said towing vehicle being turned off and sending asignal to a brake control unit via said communication bus instructingsaid brake control unit to power down.
 19. The method of claim 18,further comprising receiving a signal relating to detection of ignitionof said towing vehicle being turned on and sending a signal to saidbrake control unit to power up.
 20. The method of claim 1, furthercomprising receiving a signal relating to a lack of activity on saidcommunication bus of said towing vehicle and sending a signal to a brakecontrol unit via said communication bus instructing said brake controlunit to power down.
 21. The method of claim 20, further comprisingreceiving a signal relating to detection of activity on saidcommunication bus of said towing vehicle and sending a signal to saidbrake control unit to power up.
 22. The method of claim 1, furthercomprising performing at least one of a limited operating strategy, anautomatic adjustment of output based on variable inputs from said towingvehicle, an inductive and resistive load testing, an internal shortcircuit protection procedure, and a gain button and scroll stuckroutine.
 23. The method of claim 22, wherein performing said limitedoperating strategy comprises operating said brakes of said towed vehicledespite unavailability of a main input.
 24. The method of claim 22,wherein performing said automatic adjustment of output based on variableinputs from said towing vehicle comprises continuously sampling supplyvoltage and adjusting said second signal based on said sampling.
 25. Themethod of claim 22, wherein performing said inductive and resistive loadtesting comprises sensing load of said brakes of said towed vehicle todetermine if said load is normal and sensing if said brakes areavailable on said towed vehicle.
 26. The method of claim 22, whereinperforming said gain button and scroll stuck routine comprisescontinuously sampling inputs activated by an operator and determining ifsaid inputs are real or an electrical failure.
 27. A method forcontrolling braking of a towed vehicle, said method comprising:receiving a first signal relating to at least one of an operatingcondition of a towing vehicle, a manual input, and an operatingcondition of a towed vehicle, said first signal being received via acommunication bus of said towing vehicle; sending a second signal tobrakes of said towed vehicle, said second signal based on said firstsignal; sending a third signal to said towing vehicle via saidcommunication bus, said third signal relating to said operatingcondition of at least one of said towing vehicle and said towed vehicle;and storing said third signal in a memory.
 28. The method of claim 27,further comprising generating a brake output signal to said brakes ofsaid towed vehicle based on said second signal.
 29. The method of claim28, further comprising sending a fourth signal to said towing vehiclevia said communication bus, said fourth signal relating to saidoperating condition of at least one of said towing vehicle and saidtowed vehicle.
 30. The method of claim 29, further comprising modifyingsaid brake output signal based on said fourth signal.
 31. The method ofclaim 30, further comprising storing each ignition cycle of said towingvehicle in said memory.
 32. The method of claim 31, further comprisingusing variable length data grouping in storing each ignition cycle. 33.The method of claim 32, further comprising using an end of configurationmarker in storing each ignition cycle.
 34. The method of claim 33further comprising using said end of configuration marker to initializeoperating variables and diagnostic information for each subsequentignition cycle.
 35. A brake control unit comprising: a processor; afirst signal relating to at least one of an operating condition of atowing vehicle, a manual input, and an operating condition of a towedvehicle, said first signal sent to said processor via a communicationbus of said towing vehicle; and a second signal sent by said processorto brakes of said towed vehicle, said second signal based on said firstsignal.
 36. The brake control unit of claim 35, further comprising athird signal sent to said towing vehicle from said processor via saidcommunication bus, said third signal relating to said operatingcondition of at least one of said towing vehicle and said towed vehicle.37. The brake control unit of claim 36, wherein said brake control unitis integrated with said towing vehicle.
 38. The brake control unit ofclaim 37, wherein said towing vehicle includes a dash having dashlighting elements and wherein said display is integrated with said dashof said towing vehicle.
 39. The brake control unit of claim 38, whereinsaid display includes lighting that is adjustable to match said dashlighting elements of said towing vehicle.
 40. The brake control unit ofclaim 39, wherein said display includes a display for a towed vehicleconnected state and a towed vehicle disconnected state.
 41. The brakecontrol unit of claim 35, further comprising a controlled area networkcommunication device to communicate with a controlled area network ofsaid towing vehicle.
 42. The brake control unit of claim 35, furthercomprising a manual input device, wherein said manual input device iscapable of changing configuration of said brake control unit fromelectric to electric over hydraulic.
 43. A brake control unitcomprising: a first signal sent from a towing vehicle's communicationbus, said first signal relating to at least one operating condition ofsaid towing vehicle and said towed vehicle; a processor capable ofreceiving said first signal; a second signal sent from said processor tobrakes of a towed vehicle, said second signal based on said firstsignal; a third signal sent to said towing vehicle from said processor,said third signal based on a failure of at least one of said towingvehicle, said towed vehicle, and said brake control unit; and memoryoperably coupled to said processor to store said third signal.
 44. Thebrake control unit of claim 43, wherein said memory stores informationrelating to at least one of number of ignition cycles of towing vehicle,gain adjustments, number of manual activations, vehicle identificationnumber of towing vehicle, calibration data, and defect codes of saidtowing vehicle.
 45. The brake control unit of claim 43 wherein saidmemory stores variables for future use.
 46. The brake control unit ofclaim 45, wherein said variables include at least one of gain setting,manual override setting, towed vehicle diagnostic codes, and brakecontrol unit diagnostic codes.
 47. A method for controlling braking of atowed vehicle, said method comprising: receiving a first signal via acommunication bus of a towing vehicle, said first signal relating toanti-lock brakes of said towing vehicle; sending a second signal tobrakes of said towed vehicle, said second signal based on said firstsignal; releasing said brakes to prevent wheels of said towed vehiclefrom locking; and reapplying said brakes of said towed vehicle based onsaid first signal.